1. Field of the Invention
The present invention relates to a clock signal generating circuit, an image forming apparatus, and a clock signal generating method of the clock signal generating circuit.
2. Description of the Related Art
In general, an electronic device generates and emits electromagnetic waves. Such an electronic device may affect operation of another device by such electromagnetic waves, unless a suitable method is implemented for preventing generation and/or emission of electromagnetic waves. Such disruption of operation of an electronic device caused by undesired emission of electromagnetic waves may be referred to as electromagnetic interference (EMI). EMI can be an external factor that may cause, for example, deterioration of a function, a malfunction, an interruption, or loss of data in an electronic device.
Many countries have adopted some regulations and/or standards on electromagnetic radiation so as to prevent EMI. In a country that has adopted an EMI regulation, selling and/or using a device that does not comply with the regulation may be prohibited.
In general, when a clock generator in an electronic device oscillates in a single frequency, energy of a clock signal may be increased. A technique for spreading energy has been known such that a frequency of a clock signal is slightly modulated (i.e., frequency modulation), and thereby a peak level of the energy of the clock signal may be reduced to be a lower level. Such a technique may be referred to as “spread spectrum.” A generator for which this technique is adopted may be referred to as a “spread spectrum clock generator” (which is referred to as “SSCG,” hereinafter). A SSCG may be a component that complies with an EMI regulation.
Patent Document 1 (Japanese Unexamined Patent Publication No. 2003-140615) discloses a spread spectrum clock signal generating circuit.